This invention relates to vision substitution systems and, particularly, to tactile vision substitution systems.
A number of different approaches have been proposed to restore lost vision or to augment existing vision, including visual prosthesis and visual substitution.
Visual prosthesis usually consists of an implanted neural stimulator coupled to an externally-worn camera. Visual prosthetics may provide some restoration of sight for persons who were originally sighted but who lost vision as a result of degenerative eye disease, and success in providing sight to a blind person by way of a visual prosthesis depends upon how the person lost sight. Retinal prosthesis has been proposed and is under development by a number of organizations. This approach may be most successful where loss of vision resulted from degeneration of photoreceptors, and where the optic nerve was fully developed prior to onset of blindness; such degenerative diseases include, for example, retinitis pigmentosa and age-related macular degeneration. Prosthetic systems employing a subretinally implanted microchip are under development by Daniel V. Palanker's research organization at Stanford University, described, for example, in D. Palanker et al. (2005) “Design of a high-resolution optoelectronic retinal prosthesis”, J. Neural Eng., Vol. 2, pp. S105-S120; in D. V. Palanker et al. U.S. Pat. No. 7,047,080, titled “Self-sufficient retinal prosthesis powered by intraocular photovoltaic cells”; and in D. V. Palanker U.S. Pat. No. 7,447,547, titled “Neural prosthesis based on photomechanical deflectors and tactile sensory cells”. Robert Greenberg and coworkers associated with Second Sight Medical Products, Inc. have proposed an implanted retinal microelectrode array, described for example in Robert Greenberg et al. U.S. Pat. Nos. 7,263,403, and 7,499,754, titled “Retinal prosthesis”. Alan Y. Chow and coworkers associated with Optobionics Corporation have proposed a subretinally implanted microphotodiode array for treatment of retinitis pigmentosa, described for example in Alan Y. Chow et al. (2004) “The Artificial Silicon Retina Microchip for the Treatment of Vision Loss From Retinitis Pigmentosa”, Arch. Ophthalmol., Vol. 122, pp. 460-469.
Retinal prosthesis requires surgical intervention, and carries risks associated with implant technologies as well as risks associated with operating an electronic device in close association with nerve tissues. As noted above, visual prosthesis is suitable for persons who were originally sighted and thereafter lost vision owing to degenerative disease. Because the prosthesis is deployed within the eye, it is useful principally for treatment of vision impairment, and is not desired for vision enhancement in sighted persons.
For these reasons, vision substitution approaches may be preferred. Generally, loss of vision results from impairment of the person's capacity to transmit sensory information from the retina to the brain. In a vision substitution system, vision is restored by coupling the intact vision processing pathways with data obtained from another sensory mode such as touch. By sensory substitution, information from touch receptors is relayed to the visual cortex, where it is interpreted and perceived as an image. In a vision substitution system an image capture device (such as a digital camera) generates a signal representing a received image; the signal is processed and relayed to an array of stimulators that are disposed to stimulate touch receptors in an area of the subject's body. Some examples of vision substitution systems follow.
Paul Bach-y-Rita proposed a vision substitution system in which an electrotactile display comprising an array of electrodes is disposed on the tongue of the subject. See, e.g., Paul Bach-y-Rita et al. (1998), “Form Perception with a 49-point electrotactile stimulus array on the tongue: A technical note”, Jour. Rehabilitation Research and Development; and Paul Bach-y-Rita et al. U.S. Pat. No. 6,430,450, titled “Tongue-based tactile output device”. K. Kasmarek and coworkers at the University of Wisconsin have continued developmental work on electrotactile stimulation. A prototype electrotactile tongue display system includes a tongue display unit, a controller, and a camera; and efforts to develop a device suitable for commercial introduction are underway at Wicab, Inc. The system can provide grey scale information, but does not provide color information. The device cannot be used while the tongue is otherwise disposed, as for example while the person is eating or speaking.
Methods used to present visual, auditory, and modified tactile information to the skin were reviewed in Kurt A. Kaczmarek et al. (January 1991) “Electrotactile and Vibrotactile Displays for Sensory Substitution Systems”, IEEE Trans. Biomed. Eng., Vol. 38, No. 1. Tactile stimuli may be mechanotactile, electrotactile or thermotactile.
The Russian Republic Foundation of assistance to the blind and visually impaired (“Varesk”) is developing a tactile vision system having a tactile display attached on the subject's back. The display includes an array of electrodes. A camera receives an image and sends a signal representing the image to a computer; the computer processes the signal and delivers electrical pulses to the electrodes in the array.
A research group at the Kirchhoff-Institut fur Physik, Ruprecht-Karls-Universitat Heidelberg (Heidelberg) has presented a tactile vision substitution system that employs a “virtual tactile display” (VTD) that receives data either from camera systems equipped with suitable image processing capabilities. See, Thorsten Maucher et al., “The Heidelberg Tactile Vision Substitution System”, paper presented at the ICCHP2000, Karlsruhe, July 2000. The VTD includes a movable tactile output unit having tactile elements, each having movable piezoelectric actuators arranged in a standard Braille matrix. The tactile output unit is scanned over a large pad area. The system includes CMOS cameras and dedicated VLSI chips for image acquisition and pre-processing. Heidelberg has additionally proposed a pneumatic tactile display, in which tactile stimuli are applied to the skin by an array of compressed-air driven pistons. Reference is made to the Heidelberg site at <http://www.kip.uni-heidelberg.de/>